Analysing and machining an optical profile

An apparatus for machining an optical profile of a workpiece on a machine, the apparatus comprising:

• a simulation module configured to:
• receive nominal optical profile data representing a desired profile of a desired workpiece as designed in an initial design step;
• receive machining data corresponding to machining capabilities of the machine;
• simulate a machining of the workpiece as a function of the nominal optical profile data and the machining data, to obtain a simulated profile data;
• identify optical characteristics of the simulated profile data;
• output the identified optical characteristics to a design module, in order to enable the design module to take into account the identified optical characteristics in a further iterative design step of the desired workpiece.

A method for analysing at least one measured optical profile of a machined workpiece, comprising:

• an analysis module:
• receiving nominal optical profile data representing a desired profile of a workpiece as designed in a current design step;
• receiving a plurality of measured optical profile data corresponding to a plurality of machined workpieces;
• for each measured optical profile data, determining a difference between the measured optical profile data and the nominal optical profile data;
• removing non-systematic machining errors from the determined difference, by determining an average of the plurality of determined differences;
• and
• outputting the determined average, corresponding to errors on the profile due to machining which are systematic machining errors, to a design module, in order to enable the design module to take into account the systematic machining errors in a further design step of the desired workpiece.